Dynamic range improvements in lidar applications

ABSTRACT

A LIDAR system includes a detector array comprising a first detector region and a second detector region, wherein the first detector region comprises a first detector and the second detector region comprises a second detector, at least one optical element configured to separate light received at the at least one optical element into a first portion and a second portion, incident on the first detector and the second detector, respectively, wherein the at least one optical element is configured to alter a characteristic of the light, and a circuit configured to receive a first detection signal from the first detector responsive to the first portion of the light that is incident thereon and a second detection signal from the second detector responsive to the second portion of the light that is incident thereon, and to generate an improved signal based on the first and second detection signals.

CLAIM OF PRIORITY

This application claims priority from U.S. Provisional PatentApplication No. 62/819,889 entitled “DYNAMIC RANGE IMPROVEMENTS IN LIDARAPPLICATIONS” filed Mar. 18, 2019, the entire contents of which areincorporated by reference herein.

FIELD

The present disclosure is directed to Light Detection and Ranging(LIDAR) systems, and more particularly, to methods and devices toincrease dynamic range in time-of-flight LIDAR systems.

BACKGROUND

Time of flight (ToF) based imaging is used in a number of applicationsincluding range finding, depth profiling, and 3D imaging (e.g., LightDetection And Ranging (LIDAR)). ToF 3D imaging systems can becategorized as indirect ToF or direct ToF systems. Direct ToFmeasurement includes directly measuring the length of time betweenemitting radiation by an emitter element of a LIDAR system, and sensingthe radiation after reflection from an object or other target by adetector element of the LIDAR system. From this, the distance to thetarget can be determined. In specific applications, the sensing of thereflected radiation may be performed using a detector array ofsingle-photon detectors, such as a Single Photon Avalanche Diode (SPAD)detector array. SPAD detector arrays may be used as solid-statedetectors in imaging applications where high sensitivity and timingresolution are desired.

A SPAD is based on a p-n junction device biased beyond its breakdownregion, for example, by or in response to a strobe signal having adesired pulse width. The high reverse bias voltage generates asufficient magnitude of electric field such that a single charge carrierintroduced into the depletion layer of the device can cause aself-sustaining avalanche via impact ionization. The avalanche isquenched by a quench circuit, either actively or passively, to allow thedevice to be “reset” to detect further photons. The initiating chargecarrier can be photo-electrically generated by means of a singleincident photon striking the high field region. It is this feature whichgives rise to the name ‘Single Photon Avalanche Diode’. This singlephoton detection mode of operation is often referred to as ‘GeigerMode’.

SUMMARY

Some embodiments described herein are directed to LIDAR systems, andmore particularly, to methods and devices to increase dynamic range intime-of-flight LIDAR systems.

According to some embodiments, a LIDAR system includes a first detectorregion comprising a first detector, a second detector region comprisinga second detector, and at least one optical element configured toreceive incoming light and separate the incoming light into a firstportion and a second portion. The at least one optical element may beconfigured to direct the first portion of light to be incident on thefirst detector and the second portion of light to be incident on thesecond detector, and the at least one optical element is configured toalter the incoming light such that a characteristic of the first portionof light is different from the second portion of light.

In some embodiments, the LIDAR system further includes a control circuitconfigured to receive a first detection signal from the first detectorresponsive to the first portion of the light that is incident thereonand a second detection signal from the second detector responsive to thesecond portion of the light that is incident thereon, and to generate animproved signal based on the first and second detection signals.

In some embodiments, wherein the control circuit is further configuredto generate the improved signal based on determining that the firstdetector is saturated and, responsive thereto, preferentially using thesecond detection signal from the second detector to generate theimproved signal.

In some embodiments, the improved signal has an increased dynamic rangewith respect to the first detection signal.

In some embodiments, the characteristic of the light is an intensity ofthe light.

In some embodiments, the second portion of light has an intensity thatis less than the first portion of light.

In some embodiments, the first detector and the second detector arewithin a detector array, and the second detector region is located at aperipheral portion of the detector array.

In some embodiments, the at least one optical element comprises aneutral density filter.

In some embodiments, the first detector and/or the second detector is aSingle Photon Avalanche Diode (SPAD).

According to some embodiments, a LIDAR system includes a detector arraycomprising a first detector region and a second detector region, whereinthe first detector region comprises a first detector and the seconddetector region comprises a second detector, at least one opticalelement configured to separate light into a first portion and a secondportion, incident on the first detector and the second detector,respectively, wherein the at least one optical element is configured toalter a characteristic of the light, and a circuit configured to receivea first detection signal from the first detector responsive to the firstportion of the light that is incident thereon and a second detectionsignal from the second detector responsive to the second portion of thelight that is incident thereon, and to generate an improved signal basedon the first and second detection signals.

In some embodiments, the characteristic of the light is an intensity ofthe light.

In some embodiments, the second portion has an intensity that is lessthan the first portion.

In some embodiments, the second detector region is located at aperipheral portion of the detector array.

In some embodiments, the improved signal has an increased dynamic rangewith respect to the first detection signal.

In some embodiments, the at least one optical element comprises aneutral density filter.

In some embodiments, the LIDAR system further includes comprising anoptical emitter, and wherein the light separated by the at least oneoptical element comprises light emitted by the optical emitter andreflected by a target.

In some embodiments, the at least one optical element is configured toattenuate the light into the first portion having a first intensity andthe second portion having a second intensity, different than the firstintensity.

In some embodiments, the first detector and/or the second detector is aSingle Photon Avalanche Diode (SPAD).

According to some embodiments, a method of operating a LIDAR systemincludes receiving light at a detector array of the LIDAR system, thedetector array comprising a first detector region and a second detectorregion, wherein the first detector region comprises a first detector andthe second detector region comprises a second detector, separating thelight into a first portion and a second portion, wherein the secondportion has at least one characteristic that is different from the firstportion, directing the first portion of the light onto the firstdetector, directing the second portion of the light onto the seconddetector, and generating an improved signal based on a first detectionsignal from the first detector and a second detection signal from thesecond detector.

In some embodiments, the at least one characteristic of the lightcomprises an intensity of the light.

In some embodiments, the second portion has an intensity that is lessthan the first portion.

In some embodiments, the second detector region is located at aperipheral portion of the detector array.

In some embodiments, the improved signal has an increased dynamic rangewith respect to the first detection signal.

In some embodiments, separating the light into the first portion and thesecond portion is performed by at least one optical element comprising aneutral density filter.

In some embodiments, the at least one optical element is configured toattenuate the light into the first portion having a first intensity andthe second portion having a second intensity, different than the firstintensity.

In some embodiments, the first detector and/or the second detector is aSingle Photon Avalanche Diode (SPAD).

In some embodiments, generating the improved signal comprisesdetermining that the first detector is saturated and, responsivethereto, preferentially using the second detection signal from thesecond detector to generate the improved signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more apparent in view of the attacheddrawings and accompanying detailed description in which the samereference numerals or the same reference designators denote the sameelements throughout the specification.

FIG. 1A is a block diagram illustrating an example lidar system orcircuit in accordance with some embodiments of the present disclosure.

FIG. 1B is a block diagram illustrating the control circuit of FIG. 1Ain greater detail in accordance with some embodiments of the presentdisclosure.

FIG. 2 illustrates an example optical system according to someembodiments described herein.

FIG. 3 illustrates an example of a beam splitter according to someembodiments described herein.

FIG. 4 illustrates a method to determine a range to a target accordingto some embodiments described herein.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein withreference to lidar applications and systems. A lidar system may includean array of emitters and an array of detectors, or a system having asingle emitter and an array of detectors, or a system having an array ofemitters and a single detector. As described herein, one or moreemitters may define an emitter unit, and one or more detectors maydefine a detector pixel. A flash lidar system may acquire images byemitting light from an array, or a subset of the array, of emitterelements for short durations (pulses) over a field of view (FOV) orscene. A non-flash or scanning lidar system may generate image frames byraster scanning light emission (continuously) over a field of view orscene, for example, using a point scan or line scan to emit thenecessary power per point and sequentially scan to reconstruct the fullfield of view FOV.

An example of a ToF measurement system or circuit 100 in a LIDARapplication that may operate in accordance with embodiments of thepresent disclosure is shown in FIG. 1A. The system or circuit 100includes a control circuit 105, a timing circuit 106, an emitter array115 including a plurality of emitters 115 e, and a detector array 110including a plurality of detectors 110 d. The detectors 110 d includetime-of-flight sensors (for example, an array of single-photondetectors, such as SPADs). One or more of the emitter elements 115 e ofthe emitter array 115 may define emitter units that respectively emitoptical illumination pulses or continuous wave signals (generallyreferred to herein as optical signals or emitter signals) at a time andfrequency controlled by a timing generator or driver circuit 116. Inparticular embodiments, the emitters 115 e may be pulsed light sources,such as LEDs or lasers (such as vertical cavity surface emitting lasers(VCSELs)). The optical signals are reflected back from a target 150, andsensed by detector pixels defined by one or more detector elements 110 dof the detector array 110. The control circuit 105 may implement a pixelprocessor that measures and/or calculates the time of flight of theillumination pulse over the journey from emitter array 115 to target 150and back to the detectors 110 d of the detector array 110, using director indirect ToF measurement techniques.

In some embodiments, an emitter module or circuit 115 may include anarray of emitter elements 115 e (e.g., VCSELs), a corresponding array ofoptical elements 113,114 coupled to one or more of the emitter elements(e.g., lens(es) 113, such as microlens(es) and/or diffusers 114), and/ordriver electronics 116. The optical elements 113, 114 may be optional,and can be configured to provide a sufficiently low beam divergence ofthe light output from the emitter elements 115 e so as to ensure thatfields of illumination of either individual or groups of emitterelements 115 e do not significantly overlap, and yet provide asufficiently large beam divergence of the light output from the emitterelements 115 e to provide eye safety to observers.

The driver electronics 116 may each correspond to one or more emitterelements, and may each be operated responsive to timing control signalswith reference to a master clock and/or power control signals thatcontrol the peak power of the light output by the emitter elements 115e, for example, by controlling the peak drive current to the emitterelements 115 e. In some embodiments, each of the emitter elements 115 ein the emitter array 115 is connected to and controlled by a respectivedriver circuit 116. In other embodiments, respective groups of emitterelements 115 e in the emitter array 115 (e.g., emitter elements 115 e inspatial proximity to each other), may be connected to a same drivercircuit 116. The driver circuit or circuitry 116 may include one or moredriver transistors configured to control the modulation frequency,timing, and/or amplitude/power level of the optical signals that areoutput from the emitters 115 e.

In some embodiments, a receiver/detector module or circuit 110 includesan array of detector pixels (with each detector pixel including one ormore detectors 110 d, e.g., SPADs), receiver optics 112 (e.g., one ormore lenses to collect light over the FOV 190), and receiver electronics(including timing circuit 106) that are configured to power, enable, anddisable all or parts of the detector array 110 and to provide timingsignals thereto. The detector pixels can be activated or deactivatedwith at least nanosecond precision, and may be individually addressable,addressable by group, and/or globally addressable. The receiver optics112 may include one or more macro lens(es) that are configured tocollect light from the largest FOV that can be imaged by the lidarsystem, microlenses to improve the collection efficiency of thedetecting pixels, and/or anti-reflective coating to reduce or preventdetection of stray light. In some embodiments, a spectral filter 111 maybe provided to pass or allow passage of ‘signal’ light (i.e., light ofwavelengths corresponding to those of the optical signals output fromthe emitters) but substantially reject or prevent passage of non-signallight (i.e., light of wavelengths different than the optical signalsoutput from the emitters).

The detectors 110 d of the detector array 110 are connected to thetiming circuit 106. The timing circuit 106 may be phase-locked to thedriver circuitry 116 of the emitter array 115. The sensitivity of eachof the detectors 110 d or of groups of detectors may be controlled. Forexample, when the detector elements include reverse-biased photodiodes,avalanche photodiodes (APD), PIN diodes, and/or Geiger-mode AvalancheDiodes (SPADs), the reverse bias may be adjusted, whereby, the higherthe overbias, the higher the sensitivity. When the detector elements 110d include integrating devices such as a CCD, CMOS photogate, and/orphoton mixing device (pmd), the charge integration time may be adjustedsuch that a longer integration time translates to higher sensitivity.

Light emission output from one or more of the emitters 115 e impinges onand is reflected by one or more targets 150, and the reflected light isdetected as an optical signal (also referred to herein as a returnsignal, echo signal, or echo) by one or more of the detectors 110 d(e.g., via receiver optics 112), converted into an electrical signalrepresentation (referred to herein as a detection signal), and processed(e.g., based on time of flight) to define a 3-D point cloudrepresentation 170 of the field of view 190. Operations of lidar systemsin accordance with embodiments of the present disclosure as describedherein may be performed by one or more processors or controllers, suchas the control circuit 105 of FIG. 1A.

FIG. 1B illustrates the control circuit 105 in greater detail. Thecontrol circuit 105 may include one or more control circuits, forexample, an emitter control circuit (also referred to as an emittercircuit) that is configured to provide the emitter control signals viathe driver circuitry 116 of the emitter array 115, and/or a detectorcontrol circuit (also referred to as a detector circuit) that isconfigured to provide the detector control signals via the timingcircuitry 106 of the detector array 110 as described herein. ‘Strobing’as used herein may refer to the generation of control signals (alsoreferred to herein as strobe signals or ‘strobes’) that control thetiming and/or duration of activation (detection windows or strobewindows) of one or more detector pixels of the system or circuit 100.For example, the detector control signals output from the controlcircuit 105 may be provided to a variable delay line of the timingcircuitry 106, which may generate and output the strobe signals with theappropriate timing delays to the detector array 110. The control circuit105 is also configured to provide or control the generation ofadditional detector control signals (also referred to herein as subpixelcontrol signals) that selectively activate individual detectors 110 d ina pixel, to control the number of active detectors 110 d within thepixel. The control circuit 105 may also include processing circuit thatreceives and processes the detection signals output from the detectorarray 110 to calculate the time of flight of an illumination pulse basedthereon, and/or a sequencer circuit that is configured to coordinateoperation of the emitters 115 e and detectors 110 d. More generally, thecontrol circuit 105 may include one or more circuits that are configuredto coordinate the timing and durations of operation of the emitters 115e and/or the detectors 110 d (at the pixel level and/or at theindividual detector level), e.g., for the respective strobe windowsbetween the pulses of the optical signals from the emitters 115 e,and/or to process the detection signals output from the detectors 110 din response.

As noted above, a detection window or strobe window may refer to therespective durations of activation and deactivation of one or moredetector pixels (e.g., responsive to respective strobe signals from acontrol circuit) over the temporal period or time between pulses of theemitter(s) (which may likewise be responsive to respective emittercontrol signals from a control circuit). The time between pulses (whichdefines a laser cycle, or more generally emitter pulse frequency) may beselected or may otherwise correspond to a desired imaging distance rangefor the lidar system. The distance range may be shorter or equal to thedistance traversed by light during the time between pulses of theoptical signals. Each strobe window may be differently delayed relativeto the emitter pulses, and thus may correspond to a respective portionor subrange of the distance range. Each strobe window may alsocorrespond to a respective image acquisition subframe (or moreparticularly, point cloud acquisition subframe, generally referred toherein as a subframe) of an image frame. That is, each image frameincludes a plurality of subframes, each of the subframes samples orcollects data (e.g., as an accumulation of photons) for a respectivestrobe window over the temporal period, and each strobe window covers orcorresponds to a respective distance subrange of the distance range. Asubframe may be read out before moving the strobe window to a newdistance range. Range measurements and strobe window subrangecorrespondence as described herein are based on time of flight of anemitted pulse.

As discussed herein, detector elements 110 d may include SPADs thatundergo an avalanche in response to detecting a photon, which may besubsequently quenched. While an avalanche in a SPAD is being quenchedand the bias is being restored, the SPAD cannot detect photons. Photonsthat reach the SPAD 110 d during this period are not counted. As thenumber of photons incident on the SPAD increases, the amount of time inwhich the SPAD is unable to detect additional photons may also increase.At this point the SPAD may begin to saturate. If the light levelcontinues to increase, the SPAD may undergo avalanche as soon as bias isrestored to the SPAD, and the count rate may be limited by the avalancherecovery time.

In situations where a given target contains bright lights and or highlyreflective elements (also known as retroreflectors), the increasedintensity of the bright light and/or the echo signal from the reflectivesurface may lead to saturation of the SPADs 110 d of the detector array110. With highly saturated images, obtaining the necessary informationto estimate the phase background may be difficult due to inabilityand/or difficulty to accurately gauge the full intensity of the objects(e.g., the illumination of the objects by the emitter signal).Techniques to minimize and/or accommodate saturation and/or excessivelyintense signals may include additional processing and/or additionalsampling intervals. Examples of such techniques are included incommonly-owned U.S. Patent Publication No. 2020/0072946 entitled “GLAREMITIGATION IN LIDAR APPLICATIONS,” published on Mar. 5, 2020, to Fisheret al., the contents of which are incorporated by reference herein. Insome embodiments, saturation may be addressed by using additional (e.g.,two) exposure times within the ToF system, which may provide an increasein dynamic range.

Some embodiments of the present invention may arise from recognitionthat the dynamic range of a ToF system may be increased by utilizingadditional detectors 110 d in a detector array 110 (e.g., a SPAD array)to simultaneously sample arriving light at different intensity levels.In particular, embodiments described herein provide methods and relateddevices that are operable to separate incoming light into two or morecomponent beams having different intensities such that differentintensity levels of the light may be sampled by different respectiveSPAD detectors. In some embodiments additional SPAD detectors configuredto sample the different intensity levels of light may be located in aphysically separate SPAD array and/or on a physically separate portionof the ToF detector apparatus.

In some embodiments, incident light arriving at the detector (e.g., theecho signal) may be separated into a plurality of components, such aslight portions and/or beams, some of which may be attenuated withrespect to the original arriving light. For example, incident lightarriving at the ToF detector apparatus may be separated into a firstportion/beam having a first intensity (e.g., 90%) of the original lightand a second portion/beam having a second intensity, lower than thefirst intensity (e.g., 10%), of the original light. The firstportion/beam of the arriving light may be directed to one or more firstSPAD detectors, and the second portion/beam of the arriving light may bedirected to one or more second SPAD detectors. The ToF system may beconfigured to correlate the two portions of light (e.g., the detectedphotons at the first and second detectors) for comparison. In the eventthe first portion of light (e.g., at 90% of the intensity) results insaturation of the first detector, the second detector receiving thesecond portion of light may be utilized to determine an accurateintensity for the arriving light. Because the second portion of thelight has been attenuated to a lower intensity than the first portion(e.g., 10% of the original intensity), the second detector has a higher(e.g., ten times higher) range and/or tolerance for saturation. Forexample, a level of light that saturates the first detector at 90%intensity may not saturate the second detector at 10% intensity.

By incorporating the signals from both the first detector and the seconddetector, a dynamic range of the ToF system may be increased. Forexample, a controller and/or circuit coupled to both the first detectorand the second detector may determine that the first detector issaturated. Responsive to this determination, the controller and/orcontrol circuit may use the output of the second detector either inaddition to, or as an alternative to, the first detector. For example,in some embodiments, the controller and/or control circuit may calculateinformation (e.g., a target location) based on the second detectorresponsive to an indication of saturation at the first detector. In someembodiments, the calculation may take into account a scaling factor thatmay be used to adjust the information output from the second detectorbased on a known and/or determined attenuation of the light provided tothe second detector.

In some embodiments, detectors on peripheral portions of the ToF systemmay be used. In some embodiments, the ToF system may have unused orsparsely used portions of the device that may be populated withadditional detectors to increase the dynamic range of the ToF system. Insome embodiments, for example, the field of view of the optics andemitter coverage may use approximately one-third of the total, active,pixelated sensor area of a ToF chip. Thus, a band of pixels centered onthe ToF chip may be used to map a 100×22 degree field of view (e.g., afield of view having a horizontal range that covers 100 degrees avertical range that covers 22 degrees). By utilizing the unused pixelbands above and below the active region through additional optics,additional data can be collected.

FIG. 2 illustrates an example optical system according to someembodiments described herein. FIG. 2 illustrates a ToF chip 230associated with three optics sets including first optics set 210, secondoptics set 215, and third optics set 220 (also referred to herein asoptical elements) to generate three portions of light as an example. Theembodiments described herein are not limited to three optics sets, butcan be any number of optics sets that can cover the ToF chip area withor without overlapping.

The ToF chip 230 may include a plurality of active regions. For example,the ToF chip 230 may include first active region 240 a, second activeregion 240 b, and third active region 240 c. Each of the active regions240 a, 240 b, 240 c may include one or more detectors 110 d. FIG. 2illustrates an example of a plurality of detectors 110 d in each of theactive regions 240 a, 240 b, 240 c, but the embodiments described hereinare not limited to the configurations of detectors 110 d illustrated inFIG. 2.

Different ones of the optics sets 210, 215, 220 may be configured todistribute incoming light to different ones of the active regions 240 a,240 b, 240 c. For example, first optics set 210 may be configured todirect incoming light to first active region 240 a. Second optics set215 may be configured to direct incoming light to second active region240 b. Third optics set 220 may be configured to direct incoming lightto second active region 240 c.

The use of multiple optics sets to map over the entire ToF chip 230active area may increase the overall system dynamic range. Individualones of the optics sets 210, 215, 220 can be fitted with mechanisms toalter characteristics of the light, such as appropriately rated neutraldensity filters, to accommodate various, slightly overlapping ranges ofsignal intensities to expand the dynamic range. As used herein, aneutral density filter includes filters that reduce or modify theintensity of all wavelengths, or colors, of light equally, giving no ornegligible changes in other aspects of the light (e.g., color). Thistechnique can also be used with the other approaches, such as that oftaking data with different exposure times, to further expand the dynamicrange.

In some embodiments, respective ones of the optics sets 210, 215, 220may utilize a different type or kind of optical element. For example, afirst optical element used within the first optics set 210 may bedifferent from an optical element used within the second and/or thirdoptics set 215, 220. Thus characteristics of light passing through thefirst optics set 210 may be different from characteristics of lightpassing through the second optics set 215 and/or the third optics set220. For example, in some embodiments the first optics set 210, thesecond optics set 215, and the third optics set 220 may not affect theintensity of the light (e.g., for dim targets), but may alter othercharacteristics of the light (e.g., frequency).

Though three separate optics sets 210, 215, 220 are illustrated in FIG.2, it will be understood that the embodiments described herein are notlimited thereto. For example, in some embodiments, a plurality of opticssets may be incorporated into a single structure. For example, a singlelens or lens element may be configured to separate incoming light into aplurality of light segments, with each of the light segments configuredto be directed to a different active area (e.g., active regions 240 a,240 b, 240 c) on the ToF chip 230.

Examples of optical elements that may be used within the first opticsset 210, the second optics set 215, and/or the third optics set 220 toseparate the incoming light into multiple portions may include beamsplitters. FIG. 3 illustrates an example of a beam splitter according tosome embodiments described herein. In some embodiments, one or moreelements of a beam splitter may include a neutral density filter toattenuate the incoming light.

As illustrated in FIG. 3, the arriving light X may be intercepted by afirst optical element 302, such as a beam splitter including a neutraldensity (or other) filter. The arriving light X may be separated into afirst portion X′ and a second portion X″ by the first optical element302. The first portion X′ may be directed to a first detector region310, and the second portion X″ may be directed to a second detectorregion 320. The first portion of light X′ may have differentcharacteristics from the incoming light X and the second portion oflight X″. For example, the first optical element may slightly attenuatethe incoming light X so that the first portion of light X′ is at 90% ofthe intensity of the incoming light X. The second portion of light X″may be at 10% of the intensity of the incoming light X. These changesare merely examples, and other changes to the characteristics of theincoming light X may be changed without deviating from the embodimentsdescribed herein. For example, in some embodiments, a frequency of theincoming light X may be separated (e.g., filtered) by the first opticalelement 302, such that the frequency components of the first portion oflight X′ are different from the incoming light X.

The first detector region 310 and/or the second detector region 320 mayeach include one more individual detectors (e.g., such as detectors 110d as illustrated in FIG. 1). In some embodiments, additional opticalelements, such as beam splitters and/or reflectors, may be utilized. Forexample, in some embodiments a second optical element 304 may be used toseparate the second portion of light X″ into further portions of light(e.g., third portion X′″) before being directed to the second detectorregion 320. In some embodiments, the second optical element 304 mayreflect and/or otherwise direct the light onto a second detector region320. In some embodiments, the different portions of light (e.g., X′, X″,X′″) may have different characteristics (e.g., different intensities)though the embodiments described herein are not limited thereto. Forexample, the second portion of light X″ and the third portion of lightX′″ may be substantially the same (e.g., in terms of color, intensity,etc.). As discussed with respect to the first optical element 302, thesecond optical element 304 may alter one or more characteristics of thelight such that the third portion of light X′″ may be different from thesecond portion of light X′.

In some embodiments, the first detector region 310 and the seconddetectors region 320 may be connected to a controller and/or controlcircuit 340 that is configured to associate a first portion of lightreceived at one or more detectors of the first detector region 310 witha second portion of light received at one or more detectors of thesecond detector region 320. In some embodiments, by utilizing thedifferences between the first and second portions of light, thecontroller and/or control circuit 340 may increase a dynamic range ofthe detected light.

For example, the control circuit 340 may be configured to correlate thefirst portion of light X′ and the third portion of light X′″ received atthe first detector region 310 and second detector region 320,respectively. In the event the first portion of light X′ (e.g., at 90%of the intensity) results in saturation of the first detector region310, the second detector region 320 receiving the third portion of lightX′″ may be utilized to determine an accurate intensity for the arrivinglight. Because the third portion of the light X′″ has been attenuated toa lower intensity than the first portion of light X′ (e.g., 10% of theoriginal intensity), the second detector region 320 has a higher (e.g.,ten times higher) range and/or tolerance for saturation.

For example, a level of light that saturates the first detector region310 at 90% intensity may not saturate the second detector region 320 at10% intensity. By incorporating the signals from both the first detectorregion 310 and the second detector region 320, a dynamic range of theToF system may be increased. For example, in some embodiments, thecontroller and/or control circuit 340 may calculate information (e.g., atarget location) based on the second detector region 320 responsive toan indication of saturation at one or more detectors of the firstdetector region 310. In some embodiments, the calculation may take intoaccount a scaling factor that may be used to adjust the informationreceived at the second detector region 320 based on a known and/ordetermined attenuation of the light provided to the second detectorregion 320.

In some embodiments, different ones of the optical elements may alter(e.g., attenuate) the incoming light X such that different ones of thefirst and second detector regions 310, 320 and/or detectors receivelight of different characteristics. Though the discussion herein hasmentioned altering an intensity of the light, it will be understood thatother characteristics of the light may be changed. For example, theoptical elements may alternatively or additionally alter the frequencyand/or phase of the light.

FIG. 4 illustrates a method 400 to determine a range to a targetaccording to some embodiments described herein. Referring to FIG. 4, themethod 400 may include operation 410 in which incoming light isseparated into two or more component beams. For example, as discussedherein, optical elements may be used to separate incoming light intomultiple portions. In some embodiments, different ones of the portionsof light may have different characteristics, such as differentintensities, frequency, etc. For example, separating the light mayinclude attenuating a portion of the light to reduce its intensity ascompared to other portions of light. The optical elements may include,for example, optic sets, beam splitters, and/or filters.

In operation 420, the respective portions of light (e.g., beams) may bedirected onto different detectors. For example a first portion of lightmay be directed to a primary detector and a second portion of light maybe directed to a secondary detector. In embodiments in which theportions of light have different intensities, a portion of lightdirected to the primary detector may have a higher intensity than aportion of light directed to the secondary detector. In someembodiments, portions of light may be modified to attenuatecharacteristics associated with detector saturation.

In operation 430, output of the primary detector may be monitored for anindication that it is saturated. For example, a ratio of a dead time fora SPAD after undergoing avalanche may be monitored.

If the primary detector is not indicated as being saturated (“N” inoperation 430), the output from the primary detector (e.g., detectionsignals in response to photons from the received portion of light) maybe used in operation 440. In a ToF system, the output from the primarydetector may be used to determine a range to an object from which theportion of light was reflected in operation 470.

If the primary detector is indicated as being saturated (“Y” inoperation 430), the output from the secondary detector may bepreferentially used in operation 450. Though FIG. 4 illustrates thateither the output from the primary detector is used or the output fromthe secondary detector is used, the embodiments described herein are notlimited thereto. In some embodiments, responsive to indicating that theprimary detector is saturated, the output from both the primary andsecondary detectors may be used.

When the output from the secondary detector is used, it may be adjusted,or results determined from the output may be adjusted, in operation 460.For example, in cases where the portion of light has been attenuated(e.g., its intensity has been reduced), the output may be scaled and/oradjusted to account for the attenuation. Operation 460 may be optionalin some embodiments. In a ToF system, the output from the seconddetector may subsequently be used to determine a range to an object fromwhich the portion of light was reflected in operation 470.

Various embodiments have been described herein with reference to theaccompanying drawings in which example embodiments are shown. Theseembodiments may, however, be embodied in different forms and should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure is thorough andcomplete and fully conveys the inventive concept to those skilled in theart. Various modifications to the example embodiments and the genericprinciples and features described herein will be readily apparent. Inthe drawings, the sizes and relative sizes of layers and regions are notshown to scale, and in some instances may be exaggerated for clarity.

The example embodiments are mainly described in terms of particularmethods and devices provided in particular implementations. However, themethods and devices may operate effectively in other implementations.Phrases such as “some embodiments,” “one embodiment,” and “anotherembodiment” may refer to the same or different embodiments as well as tomultiple embodiments. The embodiments will be described with respect tosystems and/or devices having certain components. However, the systemsand/or devices may include fewer or additional components than thoseshown, and variations in the arrangement and type of the components maybe made without departing from the scope of the inventive concepts. Theexample embodiments will also be described in the context of particularmethods having certain steps or operations. However, the methods anddevices may operate effectively for other methods having differentand/or additional steps/operations and steps/operations in differentorders that are not inconsistent with the example embodiments. Thus, thepresent inventive concepts are not intended to be limited to theembodiments shown, but are to be accorded the widest scope consistentwith the principles and features described herein.

It will be understood that when an element is referred to or illustratedas being “on,” “connected,” or “coupled” to another element, it can bedirectly on, connected, or coupled to the other element, or interveningelements may be present. In contrast, when an element is referred to asbeing “directly on,” “directly connected,” or “directly coupled” toanother element, there are no intervening elements present.

It will also be understood that, although the terms first, second, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending of the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

The terminology used in the description of the invention herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the invention. As used in the description ofthe invention and the appended claims, the singular forms “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise.

It will also be understood that the term “and/or” as used herein refersto and encompasses any and all possible combinations of one or more ofthe associated listed items. It will be further understood that theterms “include,” “including,” “comprises,” and/or “comprising,” whenused in this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Embodiments of the invention are described herein with reference toillustrations that are schematic illustrations of idealized embodiments(and intermediate structures) of the invention. As such, variations fromthe shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,the regions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the actual shape of a region of adevice and are not intended to limit the scope of the invention.

Unless otherwise defined, all terms used in disclosing embodiments ofthe invention, including technical and scientific terms, have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs, and are not necessarily limited to thespecific definitions known at the time of the present invention beingdescribed. Accordingly, these terms can include equivalent terms thatare created after such time. It will be further understood that terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe present specification and in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entireties.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of allcombinations and subcombinations of the embodiments of the presentinvention described herein, and of the manner and process of making andusing them, and shall support claims to any such combination orsubcombination.

Although the invention has been described herein with reference tovarious embodiments, it will be appreciated that further variations andmodifications may be made within the scope and spirit of the principlesof the invention. Although specific terms are employed, they are used ina generic and descriptive sense only and not for purposes of limitation.

1. A Light Detection and Ranging (LIDAR) system comprising: a firstdetector region comprising a first detector; a second detector regioncomprising a second detector; and at least one optical elementconfigured to receive incoming light and separate the incoming lightinto a first portion and a second portion, wherein the at least oneoptical element is configured to direct the first portion of light to beincident on the first detector and the second portion of light to beincident on the second detector, and wherein the at least one opticalelement is configured to alter the incoming light such that acharacteristic of the first portion of light is different from thesecond portion of light.
 2. The LIDAR system of claim 1, furthercomprising a control circuit configured to receive a first detectionsignal from the first detector responsive to the first portion of thelight that is incident thereon and a second detection signal from thesecond detector responsive to the second portion of the light that isincident thereon, and to generate an improved signal based on the firstand second detection signals.
 3. The LIDAR system of claim 2, whereinthe control circuit is further configured to generate the improvedsignal based on determining that the first detector is saturated and,responsive thereto, preferentially using the second detection signalfrom the second detector to generate the improved signal.
 4. The LIDARsystem of claim 2, wherein the improved signal has an increased dynamicrange with respect to the first detection signal.
 5. The LIDAR system ofclaim 1, wherein the characteristic of the light is an intensity of thelight.
 6. The LIDAR system of claim 1, wherein the second portion oflight has an intensity that is less than the first portion of light. 7.The LIDAR system of claim 1, wherein the first detector and the seconddetector are within a detector array, and wherein the second detectorregion is located at a peripheral portion of the detector array.
 8. TheLIDAR system of claim 1, wherein the at least one optical elementcomprises a neutral density filter.
 9. The LIDAR system of claim 1,wherein the first detector and/or the second detector is a Single PhotonAvalanche Diode (SPAD).
 10. Light Detection and Ranging (LIDAR) systemcomprising: a detector array comprising a first detector region and asecond detector region, wherein the first detector region comprises afirst detector and the second detector region comprises a seconddetector; at least one optical element configured to separate light intoa first portion and a second portion, incident on the first detector andthe second detector, respectively, wherein the at least one opticalelement is configured to alter a characteristic of the light; and acircuit configured to receive a first detection signal from the firstdetector responsive to the first portion of the light that is incidentthereon and a second detection signal from the second detectorresponsive to the second portion of the light that is incident thereon,and to generate an improved signal based on the first and seconddetection signals.
 11. The LIDAR system of claim 10, wherein thecharacteristic of the light is an intensity of the light.
 12. The LIDARsystem of claim 10, wherein the second portion has an intensity that isless than the first portion.
 13. The LIDAR system of claim 10, whereinthe second detector region is located at a peripheral portion of thedetector array.
 14. The LIDAR system of claim 10, wherein the improvedsignal has an increased dynamic range with respect to the firstdetection signal.
 15. (canceled)
 16. The LIDAR system of claim 10,further comprising an optical emitter, and wherein the light separatedby the at least one optical element comprises light emitted by theoptical emitter and reflected by a target.
 17. The LIDAR system of claim10, wherein the at least one optical element is configured to attenuatethe light into the first portion having a first intensity and the secondportion having a second intensity, different than the first intensity.18. (canceled)
 19. A method of operating a Light Detection and Ranging(LIDAR) system comprising: receiving light at a detector array of theLIDAR system, the detector array comprising a first detector region anda second detector region, wherein the first detector region comprises afirst detector and the second detector region comprises a seconddetector; separating the light into a first portion and a secondportion, wherein the second portion has at least one characteristic thatis different from the first portion; directing the first portion of thelight onto the first detector; directing the second portion of the lightonto the second detector; and generating an improved signal based on afirst detection signal from the first detector and a second detectionsignal from the second detector.
 20. The method of claim 19, wherein theat least one characteristic of the light comprises an intensity of thelight.
 21. The method of claim 19, wherein the second portion has anintensity that is less than the first portion. 22-26. (canceled)
 27. Themethod of claim 19, wherein generating the improved signal comprisesdetermining that the first detector is saturated and, responsivethereto, preferentially using the second detection signal from thesecond detector to generate the improved signal.